patch 8.2.2949: tests failing because no error for float to string conversion

Problem:    Tests failing because there is no error for float to string
            conversion.
Solution:   Change the check for failure to check for correct result.  Make
            some conversions strict in Vim9 script.
diff --git a/src/testdir/test_execute_func.vim b/src/testdir/test_execute_func.vim
index 0363717..c08b239 100644
--- a/src/testdir/test_execute_func.vim
+++ b/src/testdir/test_execute_func.vim
@@ -2,6 +2,7 @@
 
 source view_util.vim
 source check.vim
+source vim9.vim
 
 func NestedEval()
   let nested = execute('echo "nested\nlines"')
@@ -37,8 +38,9 @@
   call assert_equal("\nsomething", execute('echo "something"', 'silent!'))
   call assert_equal("", execute('burp', 'silent!'))
   if has('float')
-    call assert_fails('call execute(3.4)', 'E806:')
-    call assert_fails('call execute("echo \"x\"", 3.4)', 'E806:')
+    call assert_fails('call execute(3.4)', 'E492:')
+    call assert_equal("\nx", execute("echo \"x\"", 3.4))
+    call CheckDefExecAndScriptFailure(['execute("echo \"x\"", 3.4)'], 'E806:')
   endif
 endfunc